In today's integrated circuits (IC), the bandgap voltage of a semiconductor device can be used as a voltage reference to drive an internal linear regulator, or similar arrangement to provide predictable power. The bandgap voltage is also often used as a reference voltage for over-temperature detection and for temperature independent current generation. In general, a bandgap voltage may be commonly derived by summing the temperature positive correlated difference in base-emitter voltages of two or more bipolar devices (ΔVBE) with the temperature positive correlated base-emitter voltage of one of the bipolar devices (VBE).
The temperature positive correlated ΔVBE is a factor of thermal voltage. The ΔVBE can be a constant and independent of process tolerances. As a result, the spread of the bandgap voltage is generally dependent on the performance of the one bipolar device (e.g., transistor, etc.). In today's technologies, such as 0.35 um technologies for example, the focus is more commonly on complementary metal-oxide semiconductor (CMOS) transistors. For example, one or more parasitic PNP transistors may be used to generate the bandgap voltage reference. However, in such cases, the tolerance spread of the bandgap voltage can be larger than desired for some applications.
Currently, trimming techniques at the front end (e.g., laser fusing, etc.) or at the back end (e.g., one time programmable (OTP), PROM, etc.) of a bandgap voltage circuit are often employed to lower the spread of the bandgap voltage. One disadvantage of these techniques is that they can be costly. Additional die area is needed for the trimming circuitry, and an extra step for laser fusing, or the like, at the front end can incur more production cost.
Additionally, it can be difficult to trim the circuit if the bandgap voltage is used for over-temperature protection. It is not common to test such a circuit IC at high temperatures unless the IC is intended to be used for special applications, such as for medical or automotive applications.